Megabac 2 IM/IV Injection

✔️ Mechanism of Action

Colistimethate is a polycationic surface-active antibiotic that disrupts the bacterial cytoplasmic membrane, altering its permeability and leading to cell death. It binds to lipopolysaccharides in the outer membrane of gram-negative bacteria and also interacts with intracellular components like ribosomes. This bactericidal action is particularly effective against multidrug-resistant pathogens.

✔️ Dosage & Administration

🔹 Adults (Maintenance Dose):

9 MIU/day in 2–3 divided doses

Critically ill patients: Add a 9 MIU loading dose before maintenance

🔹 Renal Impairment (Adjust dose as follows):

🔹 Hemodialysis Patients:

Non-dialysis days: 2.25 MIU/day

Dialysis days: 3 MIU/day (post-dialysis)

🔹 Pediatric Patients:

≤40 kg: 75,000–150,000 IU/kg/day in 3 divided doses

40 kg (e.g., cystic fibrosis): Higher doses may be needed

🧒 Doses based on lean body weight.

✔️ Administration Guidelines

Intermittent IV Injection:

• Inject half the daily dose slowly over 3–5 minutes, every 12 hours

Continuous Infusion:

• Administer half the dose IV over 3–5 minutes
• Infuse the remaining dose diluted in:
• 0.9% NaCl
• 5% Dextrose (with NaCl or water)
• Lactated Ringer’s Solution
• Infuse over the next 22–23 hours

Alternative IV Method:

• Dilute the prescribed dose in 50–100 mL of 0.9% NaCl, and infuse over 30–60 minutes
• ⚠ Use freshly prepared solutions within 24 hours.

🔄 Reconstitution Instructions

• IM Injection: Reconstitute with 2 mL Water for Injection
• IV Bolus: Use 5 mL Water for Injection
• Infusion: Further dilute the reconstituted solution in 50–100 mL of 0.9% NaCl

✔️ Side Effects

Common: GI upset, dizziness, slurred speech, rash, tingling sensations

Serious:

Nephrotoxicity (↑BUN, ↑creatinine, ↓urine output)

Neurotoxicity (ataxia, paresthesia, apnea, respiratory arrest)

Hypersensitivity (rash, urticaria, anaphylaxis)

✔️ Drug Interactions

Avoid concurrent use with:

• Aminoglycosides, Polymyxins (neuromuscular toxicity risk)
• Muscle relaxants (e.g., succinylcholine, tubocurarine)
• Sodium cephalothin (nephrotoxicity risk)

✔️ Contraindications

Hypersensitivity to Colistimethate Sodium or formulation components

✔️ Precautions

• Use with extreme caution in patients with renal impairment
• Monitor function in neonates, infants, and children
• Adjust the dose appropriately to avoid toxicity
• Avoid prolonged use due to the risk of neurotoxicity and nephrotoxicity

✔️ Pregnancy & Lactation

Use only if needed during pregnancy

Not known whether excreted in breast milk – caution advised in lactation

✔️ Storage Guidelines

Before reconstitution: Store below 30°C, protect from light

After reconstitution: Store at 2°C–8°C, do not freeze, use within 24 hours